Computer Science – Sound
Scientific paper
Dec 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agufmsh53a1237s&link_type=abstract
American Geophysical Union, Fall Meeting 2005, abstract #SH53A-1237
Computer Science
Sound
2752 Mhd Waves And Instabilities (2149, 6050, 7836), 7522 Helioseismology, 7836 Mhd Waves And Instabilities (2149, 2752, 6050)
Scientific paper
Local time-distance helioseismology aims to get an information about the internal structure of subphotospheric region of the Sun, like flows and sound speed perturbations, by investigation of observed travel times of the oscillatory responses of subphotosphere to a perturbation. We present the results of simulations of acoustic wave propagation and dispersion in the non-magnetic solar subphotosphere. We use methods similar to the observational ones to produce results aiming to reproduce observational data from local helioseismology. The VAC code (G. Toth) is used to carry out the simulations. The code can solve the full system of ideal hydrodynamic equations in two or three dimensions. All the results presented are carried out in 2D. The simulations use realistic solar density and pressure stratifications and are based on fully compressible ideal hydrodynamical model. Acoustic waves are produced by perturbations located near the layer corresponding to the visible surface of the Sun. The simulation domain is 150 Mm wide and 52.6 Mm deep, and has a resolution of 600x4000 grid points; the upper boundary of the domain is near the temperature minimum. The density profile for the initial plane-parallel model is taken from Christensen-Dalsgaard's standard Model S. We suppress convective motions of the fluid in the domain by slight change of adiabatic index γ_1. This approach has an advantage among other approaches because the waves we study, while they propagate through the quiescent medium, can be clearly observed far from the source undisturbed by convective fluid motions. First we study the propagation of acoustic waves produced by a harmonic pressure perturbation, then, in order to follow the criteria of realism we introduce more involved perturbation source, described as a source in the energy equation of the HD system of equations. The source used corresponds to a localized cooling event causing mass inflow and sound waves extinction (M. Rast, 1999). In order to reproduce the helioseismogram of the quiet Sun we introduce a number of randomly distributed sources with random amplitudes and present a comparison of the simulated data with the observations.
Erdelyi Robert
Shelyag Sergiy
Thompson Michael J.
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